Condensate guiding apparatus for vertical condensing tubes of vapor condenser

ABSTRACT

Condensed refrigerant vapor that forms on the internal surface of a vertical condensing tube in a refrigeration system is removed from the upper portion of the tube by a tree-like insert having upwardly extending branches that contact the tube&#39;&#39;s internal surface and, by capillary action and gravity, guide the condensate away from the surface and down the trunk of the insert. Removing the condensate or condensed vapor improves the heat transfer characteristic of the condensing tube and enhances the condensation process. To improve efficiency, liquid subcooling is achieved by returning some of the removed condensate back to the tube&#39;&#39;s internal surface in a lower portion of the tube. This is accomplished by having the lowermost branches of the insert extend downwardly to the tube&#39;&#39;s internal surface.

United States Patent [191 Newton Sept. 9, 1975 [75] Inventor: Alwin B. Newton, York, Pa.

[73] Assignee: Borg-Warner Corporation, Chicago,

Ill.

[22] Filed: June 26, I974 [21] App]. No.: 483,195

52 U.S.Cl. 165/110; 62/115; 62/507; l65/l74; 138/38 51 1m.c1. F28b 9/08 [58] Field of Search l65/I I0, I74, 114; 62/506, 62/507, 115; 138/38 Com pressor Primary ExaminerAlbert W. Davis, Jr. Attorney, Agent, or Firm.lames E. Tracy [57] ABSTRACT Condensed refrigerant vapor that forms on the inter nal surface of a vertical condensing tube in a refrigeration system is removed from the upper portion of the tube by a tree-like insert having upwardly extending branches that contact the tubes internal surface and, by capillary action and gravity, guide the condensate away from the surface and down the trunk of the in sert. Removing the condensate or condensed vapor improves the heat transfer characteristic of the condensing tube and enhances the condensation process. To improve efficiency, liquid sub-cooling is achieved by returning some of the removed condensate back to the tubes internal surface in a lower portion of the tube. This is accomplished by having the lowermost branches of the insert extend downwardly to the tubes internal surface.

4 Claims, 2 Drawing Figures Evaporator PATENTED 55? 91975 mi 0 ...L C e m C CONDENSATE GUIDING APPARATUS FOR VERTICAL CONDENSING TUBES OF VAPOR CONDENSER BACKGROUND OF THE INVENTION Vertical condensing tubes for a refrigeration system have been developed with inserts for picking the refrigerant condensate off of the internal surfaces of the tubes and guiding it downwardly through the central cores of the tubes to a lower header or collector. By minimizing the thickness of the condensed refrigerant on the internal surfaces of the condensing tubes, the heat transfer characteristic is improved and condensation is enhanced. Prior condensate guiding systems are disclosed in copending patent applications Ser. No. 271,442, filed July 13, 1972, and Ser. No. 295,086, filed Oct. 4, 1972, now US. Pat. No. 3,837,396, granted Sept. 24, 1974, both of which were filed in the name of Alwin 8. Newton and assigned to the present assignee.

The present invention employs a uniquely constructed condensate guiding apparatus that also removes condensed refrigerant from the condensing tubes internal surfaces but in addition achieves, within the condensing tubes, sub-cooling of the liquid refrigerant. Of course, this improves the efficiency of the refrigeration system since the refrigerant leaves the vapor condenser with a much lower heat content than would otherwise be the case. As a consequence, in the evaporator of the system more heat can be absorbed by the refrigerant from the medium to the cooled.

SUMMARY OF THE INVENTION The condensate guiding apparatus of the invention is to be incorporated in a vapor condenser of the type having at least one air-cooled, generally vertical condensing tube through which refrigerant vapor to be condensed flows and forms condensate on the tube's internal surface. The guiding apparatus includes means for removing condensate from an upper portion of the tube's internal surface to improve the heat transfer chracteristic of the condensing tube and to enhance condensation. Means are also provided for returning at least some of the removed condensate to a lower portion of the tube's internal surface to obtain subcooling of the returned condensate.

DESCRIPTION OF THE DRAWING The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further advantages and features thereof, may best be understood, however, by reference to the following description in conjunction with the accompanying drawing in which:

FIG. 1 is a schematic representation, with portions broken away and in section, of a refrigeration system having a vapor condenser constructed in accordance with the invention; and,

FIG. 2 is a sectional view of part of the system of FIG. 1 and taken along the plane ofsection line 22 in FIG. 1.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT The disclosed refrigeration system, which may constitute an air conditioning system, includes a vapor condenser 10 having a series of cylindrically shaped vertical condensing tubes 11. Of course, only three such tubes are shown to avoid unduly encumbering the drawing. Preferably, the condensing tubes are aircooled which is facilitated by a series of parallel, planar cooling fins 13 attached in heat exchange relationship to the external surfaces of tubes 11. The lower ends of the vertical condensing tubes are open and communicate with a cylindrically shaped horizontal header l5. Refrigerant gas or vapor is received at inlet 17 from compressor 18 and flows through the header and upward through condensing tubes 11. Air is directed, by a fan (not shown), around the outside of the condensing tubes and between fins 13 so that sufficient heat is removed from the vapor to cause it to condense on the internal surfaces of the tubes. In a manner to be explained, the condensed vapor or condensate is guided downwardly through each condensing tube to the bottom of header 15. A cylindrically shaped outlet 21 extends into header 15 a substantial distance and is slotted or open along its bottom (see FIG. 2) so that only liquid refrigerant or condensate is drawn from the header and supplied to expansion device 23 where it expands and emerges as a mixture of liquid and gas but primarily a liquid. As the mixture than flows through evaporator 24, which is in heat exchange relation or contact with the medium to be cooled, heat is transferred from the medium to the refrigerant and the entirety of the refrigerant assumes its gaseous state. It is then compressed by compressor 18 to provide the refrigerant vapor for inlet 17.

The top ends of condensing tubes 11 are closed except for small vents that are coupled through capillary tvpe tubes 26 to a common collector 27. This arrangement provides for purging of any non-condensible components from the refrigerant vapor that flows upwardly through tubes 11. Preferably, these non-condensibles are released into the atmosphere from collector 27, although if desired they could be pumped back into the refrigeration system and recirculated.

Turning now to the condensate guiding apparatus of the invention, inserted in each of the condensing tubes is a tree-like structure or apparatus 28 having a vertical trunk 29 that extends longitudinally within and is coaxial with the tube. Attached to the upper portion of trunk 29 (roughly the upper three-fourths of the trunk) is a series of flexible bristle-like branches or spires 31 which surround the trunk in a random pattern and extend upwardly and outwardly to establish point contacts with the tubes internal surface. Branches 31 may be of different lengths and extend at different angles from trunk 29. Moreover, they may be made of metal, nylon, plastic or any suitable material. Their purpose is to pick off, by capillary action and gravity, the condensed vapor or condensate from the tubes ternal surface. Once the condensate is removed from the internal surface, it is guided downwardly along branches 31 to trunk 29 and thence downwardly along the trunk and eventually to the bottom of header 15. By 60 stripping the condensate from the internal surfaces, the

heat transferred from the refrigerant to the cooling medium on the outside of the tubes will be maximized thereby enhancing the condensation process.

Each guiding apparatus 28 is preferably made with spires or branches 31 of a length greater than the radius of the condensing tube in which it is incorporated. The branches are preferably initially constructed so as to be roughly perpendicular to trunk 29 and assume their depicted orientation during the assembly of the tube when apparatus 28 is inserted into the tube from its upper end. This method has the advantage of providing a secure mounting of apparz :us 28 within the tube as well as providing a good point contact, with a positive capillary attraction, between the free ends of the branches and the tubes internal surface.

In accordance with the invention, the lowermost branches 32 of each apparatus 28 are angled so that they extend downwardly and outwardly from trunk 29 and in point contact with the tubes internal surface. With this orientation for branches 32, some of condensate removed by branches 3] and flowing down truck 29 will be guided along branches 32 and returned to the tubes internal surface. The returned condensate is thus subjected to additional cooling or subcooling so that it arrives at the bottom of header 1S, and ultimately to expansion device 23 and evaporator 24, with a heat content much lower than it otherwise would have in the absence of the invention. As a result, more heat can be transferred to the refrigerant from the medium to be cooled.

Preferably, branches 32 and branches 31 are similarly shaped and are made of the same material. One convenient method for assembling each condensate guiding apparatus 28 to its associated condensing tube is to insert the apparatus into the tube from the top and push it downwardly until all of the lowermost branches 32 are below the lower end of the tube. Apparatus 28 is then retracted upwardly to the position shown in the drawing. [n this way, all of the branches will be angled as desired.

The invention provides, therefore, a unique apparatus for guiding condensate within and through a vertical condensing tube so as to improve the heat transfer characteristic of the tubes upper portion while at the same time achieving liquid sub-cooling in the lower portion.

Certain features described in the present application are disclosed and claimed in copending application Ser. No. 483,194, filed concurently herewith in the name of Alwin B. Newton, and assigned to the present assignee.

While a particular embodiment of the invention has been shown and described, modifications may be made, and it is intended in the appended claims to cover all such modifications as may fall within the true spirit and scope of the invention.

I claim:

1. In a vapor condenser of the type having at least one air-cooled, generally vertical condensing tube through which refrigerant vapor to be condensed flows and forms condensate on the tubes internal surface, apparatus for guiding the condensate within the condensing tube comprising:

means for removing condensate from an upper portion of the tubes internal surface to improve the heat transfer characteristic of the condensing tube and to enhance condensation;

and means for returning at least some of the removed condensate to a lower portion of the tubes internal surface to obtain sub-cooling of the returned condensate.

2. In a vapor condenser of the type having at least one air-cooled, generally vertical condensing tube through which refrigerant vapor to be condensed flows and fom'is condensate on the tubes internal surface, apparatus for guiding the condensate within the condensing tube comprising:

a generally vertical trunk extending longitudinally within the vertical condensing tube and spaced from the tubes internal surface; first series of bristle-like branches attached to an upper portion of said trunk and extending upwardly and outwardly from said trunk and in contact with the tubes internal surface to remove condensate therefrom and to guide that condensate downwardly along said first series of branches and along said trunk, thereby improving the heat transfer characteristic of the condensing tube to enhance condensation;

and a second series of bristle-like branches attached to a lower portion of said trunk and extending downwardly and outwardly from said trunk and in contact with the tubes internal surface to guide at least some of the condensate flowing down said trunk back to the tubes internal surface, thereby obtaining sub-cooling of the returned condensate.

3. Condensate guiding apparatus according to claim 2 in which said trunk is coaxial with the condensing tube and wherein said branches of both of said series are flexible and provide point contacts with the tubes internal surface.

4. Condensate guiding apparatus according to claim 2 wherein said trunk extends throughout substantially the entire length of the condensing tube, in which said first series of branches extends along at least the upper three quarters of said trunk and wherein said second series of branches extends along less than the lower one quarter of said trunk. 

1. In a vapor condenser of the type having at least one aircooled, generally vertical condensing tube through which refrigerant vapor to be condensed flows and forms condensate on the tube''s internal surface, apparatus for guiding the condensate within the condensing tube comprising: means for removing condensate from an upper portion of the tube''s internal surface to improve the heat transfer characteristic of the condensing tube and to enhance condensation; and means for returning at least some of the removed condensate to a lower portion of the tube''s internal surface to obtain sub-cooling of the returned condensate.
 2. In a vapor condenser of the type having at least one air-cooled, generally vertical condensing tube through which refrigerant vapor to be condensed flows and forms condensate on the tube''s internal surface, apparatus for guiding the condensate within the condensing tube comprising: a generally vertical trunk extending longitudinally within the vertical condensing tube and spaced from the tube''s internal surface; a first series of bristle-like branches attached to an upper portion of said trunk and extending upwardly and outwardly from said trunk and in contact with the tube''s internal surface to remove condensate therefrom and to guide that condensate downwardly along said first series of branches and along said trunk, thereby improving the heat transfer characteristic of the condensing tube to enhance condensation; and a second series of bristle-like branches attached to a lower portion of said trunk and extending downwardly and outwardly from said trunk and in contact with the tube''s internal surface to guide at least some of the condensate flowing down said trunk back to the tube''s internal surface, thereby obTaining sub-cooling of the returned condensate.
 3. Condensate guiding apparatus according to claim 2 in which said trunk is coaxial with the condensing tube and wherein said branches of both of said series are flexible and provide point contacts with the tube''s internal surface.
 4. Condensate guiding apparatus according to claim 2 wherein said trunk extends throughout substantially the entire length of the condensing tube, in which said first series of branches extends along at least the upper three quarters of said trunk and wherein said second series of branches extends along less than the lower one quarter of said trunk. 